I still believe Twitter is on the slow road to mainstream adoption, but today another micro-messaging service, Seesmic, took what should be a big leap in that direction. The service, which uses video rather than text to convey messages, has had perhaps even more questions than Twitter about its usefulness. Perhaps not anymore.

This morning The Guardian’s Jemima Kiss posted some questions aimed at the cast and crew of the new film Indiana Jones and the Kingdom of the Crystal Skull. Guess who responded? Director Steven Spielberg, Producer George Lucas and star Harrison Ford among others. Yes, they’re all there, on video, on Seesmic.

Is it a publicity stunt? Sure. But really how many things aren’t in this day and age? Yes, it might have been more interesting to see Spielberg or Ford in their pajamas answering questions rather than it being a fairly obviously more professional set up (camera on tripod, chair in front of backdrop, off-camera interviewers, etc), but we’ll take what we can get. Remember, Hollywood celebrities also have an image to maintain.

Seesmic’s founder Loic Le Meur claims that he didn’t even know it was going to happen until right before the videos went up, so he couldn’t even massively publicize it. You can bet he’s getting that publicity now. The BBC and others are already writing it up; and certainly a lot more will.

Something like this simply could not work in the same way on Twitter (which currently has no video option). Even if Spielberg, Lucas, Ford and the others were on the service, it would be very hard to tell if it was actually them behind their names, and maybe even harder to tell if they, and not their assistants, were answering questions. With Seesmic we have the iconic figures right in front of us on video.

I was fairly bullish on Seesmic early on, so it’s nice to see it living up to some of its potential. Seesmic is also the service behind many of the video comments you know see around the web, including on VentureBeat.

Spielberg in particular has proven himself to be at the forefront of a lot of interesting things going on in technology. He talks about this a bit in one of the videos below, including that he has some Internet project in the works that he can’t discuss. In another field, the early reviews of his game for the Wii, Boom Blox have been great.